In recent years, an increased number of people have experienced onset of an allergic symptom(s) caused by specific pollen(s), food(s), etc., and this has become an object of public concern. As a result, development of an anti-allergic agent or food for mitigating an onset allergic symptom continues to be an object of great interest.
Meanwhile, therapeutic methods for allergic symptoms are generally divided into steroid therapies based on, for example, administration of a steroid hormone, and non-steroid therapies employing an anti-histaminic agent or the like. Of these, steroid therapies are highly effective for mitigating allergic symptoms. However, administration of a steroid for a long period of time may cause adverse side effects such as osteoporosis, cataract, and thrombosis.
The onset mechanism of allergic symptoms has already been elucidated. Specifically, granulocytes such as basophils and mast cells contain chemical mediators such as histamine. When a specific site of the surfaces of such granulocytes is stimulated by an antigen, degranulation occurs, whereby the chemical mediators are released to the outside of the cells. The thus-released chemical mediators induce allergic symptoms such as sneezing, snivel, lacrymation, dermatitis, and asthma.
Since the onset mechanism of allergic symptoms has been elucidated, attempts, in addition to reduction in IgE level, have been made to discover a drug for non-steroid therapy from, for example, extracts of natural products. Such drugs inhibit degranulation of mast cells and basophils, which would otherwise occur through binding of IgE to a high-affinity IgE receptor (FcεRI) expressed on the surfaces of mast cells and basophils and subsequent cross-linking by an antigen.
Examples of such drugs include α- or γ-mangostin, which is present in a mangosteen peel extract (see Patent Document 1); epigallocatechin-3-O-gallates present in tea extracts (see Non-Patent Document 1); a benzophenone derivative “sulochrin” which is produced by Fungus Oospora as a kind of fungus (see Patent Document 2); a diterpene “forskolin” which is extracted from a Perilla plant (see Patent Document 3); and a phenylpropanoid extracted from dry roots of A. galanga (Thailand) (see Non-Patent Document 2).    Patent Document 1: JP-A-2000-116356    Patent Document 2: JP-A-8-92082    Patent Document 3: JP-A-2003-252786    Non-Patent Document 1: Maeda et al, The Journal of Immunology (2004), Vol. 172, pp. 4486-4492    Non-Patent Document 2: Yoshikawa et al., Research Report (2002-2003), “High-Tech Research Center” Project, Ministry of Education, Culture, Sports, Science and Technology—Japan; -Pharmacognosy-, Anti-allergic components in Natural drug of Thailand “Khaa,” [online], April 2004, Kyoto Pharmaceutical University, [retrieved: Aug. 2, 2005], Internet <URL: http://www.kyoto-phu.ac.jp/hitech/a5.pdf>